class Solution {
public:
    const int INF=0X3f3f3f3f;
    int maxProfit(vector<int>& prices) {
        int n=prices.size();

        vector<vector<int>>f(n,vector<int>(3,-INF));
        auto g=f; 
        f[0][0]=-prices[0],g[0][0]=0;
        for(int i=1;i<n;i++)
        {
            for(int j=0;j<3;j++)
            {
                f[i][j]=max(f[i-1][j],g[i-1][j]-prices[i]);//传递或者是从卖过的转移过来
                g[i][j]=g[i-1][j];
                if(j-1>=0)
                g[i][j]=max(g[i][j],f[i-1][j-1]+prices[i]);   
            }
        }
        int ret=0;
        for(int i=0;i<3;i++)
        ret=max(g[n-1][i],ret);
        return ret;
    }
};
